IPC for Data Passing

Question 1

IPC

Answer 1

Inter-Process Communication

Question 2

Pipe

Answer 2

• IPC technique for passing information to another process
• uses byte-stream
• only for use between child and parent
• one reader and one writer
• purely in-memory
• pipe is deleted after all fds closed

Question 3

Byte-Stream

Answer 3

Message that has no notion of “boundaries”. No space division between messages

Question 4

pipe()

Answer 4

int pipe( int fd[2] )
- creates a new pipe and returns two file descriptors
- f[0] is read end
- f[1] is write end

Question 5

fork()

Answer 5

Child inherits fd[0] and fd[1]

Question 6

close()

Answer 6

Closes unused file descriptors

Question 7

How do pipes work under the hood?

Answer 7

• in-memory file system,PIPEFS, in the kernel memory address space
• pipefs mounted at system initialization
• pipe corresponds to a file created in pipefs
• pipe() creates pipe and returns two file descriptors (one read and one write)

Question 8

FIFO

Answer 8

Named Pipe.
- uses byte-stream
- not limited to be used between parent and child process
- multiple writers and one reader
- file created in hard disk, but I/O through kernel memory
- not deleted after closing all fds

Question 9

Message Queues

Answer 9

Like named pipe but supports boundaries and message types/priorities

Question 10

Unix Domain Socket

Answer 10

• like a pipe combined with a message queue
• named using path name
• supports byte-stream and datagrams
• bidirectional

Question 11

Shared Memory

Answer 11

Region of physical memory that is mapped to two (or more) processes, both can edit and view same data